Sport Jet 90 leaking exhaust gasket?

[Speedling]

If the gasket is a burnable material you could be right!
I wonder if a gasket could be made of like copper or something? Copper may be a poor choice but trying to think of something metal but softer than aluminum

 

[RedBarron55]

The pictures look like a fibrous material like the carb gaskets etc.
The literature says that there is an adhesive on both sides.
I remember that on the old Chrysler valve cover gaskets on the 440s they would burn out and leak like Heck.
When I was traveling in Canada in the old Winnebago I stopped by the local Chrysler dealer to buy some more to stop the leaking for a while.
The counter man said I needed both new valve cover gaskets AND new original Chrysler Exhaust gaskets.
The ORIGINAL had metal tabs that shielded the valve cover from the heat of those exhaust manifolds that humped up past the edge of the cover.
I installed the exhaust gaskets and valve cover gaskets and NEVER had one burn out again!
The water jacket full of water should keep the mating surfaces and the gasket less than 210 F* and it should survive.
No water and the aluminum right there where the three exhausts come together COULD get hot enough to butn through.
This MIGHT be why there is so much problem with the water getting into the Sport Jets.
The manual says NEVER crank without water flowing and one excuse is that unburned fuel might well collect underneath the engine and blow up and bend the ride plate.
Another good reason would be burning out the exhaust manifold gasket!
I know that as an Authorized Aircraft Inspector (IA) I often read the Airworthiness Directives and wonder exactly why they are required and what happened. Most of the time there is no mention of why the changes have to be made.

 

[Ben Okopnik]

If the gasket is a burnable material you could be right!
I wonder if a gasket could be made of like copper or something? Copper may be a poor choice but trying to think of something metal but softer than aluminum

Many, MANY moons ago, when I was racing cars and fiddling with engines, some of the guys in the group would a) shave the heads down to get the compression ratios up, b) mix their own fuel, and c) make their own head gaskets by laying a sheet of soft copper over the faying surface and carefully tapping around all the edges with a hammer until they cut through the copper sheet (the regular "paper" gaskets couldn't stand anything like that amount of pressure.) Oh yeah - torqued the hell out of those bolts, too. Worked pretty well, as I recall.

 

[RedBarron55]

Might work. You could get a thin copper sheet and cut the gasket and then anneal it to soften it from hammering.
I am going to figure this out.
It makes no sense that the jet will fill the cylinders soooo easily!
Probably the problem is not the paper, but no cooling for the assembly until it is too late.
The new gasket making materials is good for over 600 F* and maybe just leave the gasket out and seal it with good fuel proof gasket material.
Probably not though
When it warms up a little I will take my trusty ratchet and remove the manifold as take a look. I hate to do this without the new gasket in hand, but inquiring minds want to know.

 

[RedBarron55]

Here is what I found when I pulled the manifold.
Two bolt holes were helicoiled and left proud of the surface , and would keep the gasket from sealing.
I have ground them flush, but I worry that they may not have been installed correctly and have pulled out some.
The gaskets were not "stuck" hard to the block and manifold here and this is probably where the leak is located.
I will post pictures later as the AT&T internet is down for the third day and I am using my Verizon cellphone for connection and to upload the pictures I have to email them to myself to get them on this computer.
I firmly believe that this is where the water is getting into the cylinders from.
The water to keep the rubber bellows cool comes from this manifold and is transferred by about a 1/4" tube that has ports that go to right above the bellows to keep it wet and cool. after the bellows the water runs with the exhaust under the mounting plate to the exhaust chamber and out under the boat.

 

[Speedling]

Here is what I found when I pulled the manifold.
Two bolt holes were helicoiled and left proud of the surface , and would keep the gasket from sealing.
I have ground them flush, but I worry that they may not have been installed correctly and have pulled out some.
The gaskets were not "stuck" hard to the block and manifold here and this is probably where the leak is located.
I will post pictures later as the AT&T internet is down for the third day and I am using my Verizon cellphone for connection and to upload the pictures I have to email them to myself to get them on this computer.
I firmly believe that this is where the water is getting into the cylinders from.
The water to keep the rubber bellows cool comes from this manifold and is transferred by about a 1/4" tube that has ports that go to right above the bellows to keep it wet and cool. after the bellows the water runs with the exhaust under the mounting plate to the exhaust chamber and out under the boat.

Sounds like you just about got it!
If u go the copper route sometimes a cheap and easy way to find it is copper flashing. Of course, i am a crazy masonry guy that for me means making one call and going to get it with my next load.

 

[RedBarron55]

I got the new gasket and installed it with Permatex 85420 polyurethane fuel resistant sealer.
This is good to 500*F and is non hardening and is rated for sealing water and oil.
I torqued the manifold to 100 in lbs this after noon and I will recheck it in the morning.
Also I am planning to start fiberglassing the loose parts in the flotation boxes as well.
I am not going to run the engine until I have finished the glass work to keep from having to re clean the system.
When it is time to check out the engine I plan to run the water for a while with the plugs out to make sure that there is no leakage from the cooling to the exhaust side/

 

[RedBarron55]

Bad news I am still getting water into the #3 cylinder.
I THINK I have the exhaust manifold gasket sealed, but the water is still getting in from somewhere.
Cracked block or head?
I may have to take the whole engine out and rebuild or at least take it apart to check.
Could there be blockage in the exhaust that would back the water up the exhaust elbow and into the expansion chamber?
Any suggestions appreciated.
Is it possible that there is a head gasket problem?
The compression readings are all the same at 90 + psi.
If the compression ratio is 6:1 this is good , but I can't find the CR for the engine anywhere yet.
Here is a picture of the offending helicoil

Maybe they did the same thing with the head?
If it is not raining tomorrow I may pull the head and take a look and see if I can see what the problem might be.
I wonder if you could tell what the problem might be if the transfer cover was pulled?

 

[RedBarron55]

Pulled the head this morning and I was worried about being able to get it off in the boat with little room to work.
I shouldn't have been as it fell off when the last bolt was removed.
Some of the bolts were very difficult to back out and this might have been due to not properly cleaning the threads or water leaking from the water jacket to at least the bolt holes.
Here are some pictures

 

[RedBarron55]

Today I decided to get replacement grade 8 head bolts and all I could buy were 5/16 - 18 X 2 1/2. The original should be 5/16 - 18 2 3/8 and oddly enough I found several hardware store 2 1/2 inch bolts, several correct 2 3/8 and a couple of the new style TTY single use bolts.
What are the chances that the engine builder failed to chase the threads in the block and if he did deep enough for the too long bolts?
The head gasket does not show much if any squeeze on the composite part or the metal inserts and I think that improper torque is part of the problem.
This might have been OK until the water let in by the bad seal on the exhaust manifold got a little water in the cylinders and possibly broke whatever seal there was on the #3 cylinder.
The bolts were covered with the bloom of the white corrosion you see in the aluminum, but if the gasket were properly sealed around those bolts there would be no water there for corrosion.
The last bolt on the bottom of the block was very hard to remove and I bent a 1/4" extension getting it out!

 

[RedBarron55]

Here are some observations on the operation of the Sport jet engine on the hose.
1. The system is "sealed" until the thermostat opens up except for the small holes in the nozzle that feeds water the the exhaust elbow and then sprays it back into the exhaust stream above the bellows to keep that rubber piece cool.
2. There does not seem to be any small bypass around the thermostat to the head and from there to the outlet below the engine.
This means that the only relief is those small holes in the exhaust nozzle and is the flow from the hose is greater than this the pressure will build until the opening of the thermostat.
3. If the head gasket is "loose" or blown the water will get into the cylinders.
4. If there is a blown out spot in the exhaust manifold gasket the water will get into the cylinders from the manifold through the exhaust ports.

What we need is a good low pressure water regulator for the wash out system.

Here is a guess in the difference in the flush from the consumer flush at the top and the water feed from the bottom.
The bottom emulates the water flow from the pump, but is not regulated by engine speed and power with the pressure increasing as the exhaust pressure increases. This is what I think keeps the higher pressure from the high speed operations from backing up into the exhaust manifold or blowing out the exhaust manifold gasket and also the higher pressures before the thermostat opens.
When the temp gets over 130 the water flow through it then goes to cool the head cover and head.

The top flush flushes the water from the top of the engine down the starboard side of the cylinders and around the bottom up to the top of the exhaust manifold and then down through the manifold and out of the pump.

Neither flush flushes out the head since the thermostat will be closed. The bottom flush cannot flush the head either since the thermostat does not open either (in my opinion).

Does anyone else have an observation?

Personally I think that there might ought to be a small hole drilled in the flange of the thermostat to allow some water to bypass the thermostat under any conditions. Perhaps there is a small amount of leakage designed in to allow for the escape of air to allow the block to fill?
If there is no bypass how does the water displace the air?
The outboard had a bypass but the sport jet does not seem to have one.

 

[RedBarron55]

More information.
There is a bypass in the system and it is the thermostat and spring in the housing at the top of the head cover.
The thermostat seals at a rubber seal retained by a metal ring.
The spring holds the thermostat against the seal until the pressure is great enough to open it.
If there is corrosion in the clip it could keep the thermostat from opening under pressure.
The area of the thermostat is about 1 square inch so the pressure to open is about the pressure it takes to compress the spring enough to crack the thermostat off the seal.

I think that you should regularly inspect the housing and the clearances on the clip for buildup, especially if you have cooling problems or arr having problems with the flushing filling cylinders.
remember that tie pressure from the hose is basically the city water pressure it the small holes in the feed to the exhaust cooling jacket won't flow the amount you are putting in.
It is possible that the spring could be shortened to reduce the bypass pressure.
I didn't have a way to measure the pounds of pressure to crack the thermostat open, but it would be the same to open since the area of the thermostat is right at 1"

 

[Teeko]

I know this is an old thread but did you ever find out the cause of water in the cylinders? Did you ever get it running correctly.

 

[RedBarron55]

Yes! After all of the trials and tribulations I found that the outboard engine water inlet to the exhaust manifold (bottom front side) is a 3/4" hole that should be blocked off completely by the proper sport jet gasket, but the outboard gasket was installed (incorrectly).
This let water leak from the bottom of the front side cooling jacket into the exhaust manifold where it could run into the cylinders.
I found this when I blew air at the hole with the exhaust cover off and bubbles formed in the bottom of the exhaust.
To fix this without taking off the engine and replacing the gasket I cleaned the 3/4" hole and filled it with JB weld.
No more leaks and n worrying about how hard the water was turned on the service port etc.
I suspect that this is a problem for a lot of the people who have water getting into the cylinders on sport jets.

20180109_105409

• RedBarron55
• Jan 9, 2018

If you look carefully you can see the inlet port for the outboard waaay back there on the bottom. This port has no function other tha place for the water to leak from the water jacket into the exhaust area.
Here is a picture of the outboard gasket.

And here is the correct Sport Jet gasket. Notice that that hole is fully surrounded and not open like the outboard. There is no passage underneath the engine the baseplate is solid here.